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CVE-2015-6421

23
FAUCET Score

CVE-2015-6421 describes a denial-of-service vulnerability in the cifs-ao component of Cisco Wide Area Application Services (WAAS) and Virtual WAAS (vWAAS) devices, affecting versions 5.x before 5.3.5d and 5.4/5.5 before 5.5.3. This flaw allows unauthenticated remote attackers to trigger resource exhaustion and device reloads through specially crafted network traffic. With a CVSS score of 7.5 (High), it presents a significant availability risk due to its network-based attack vector and low attack complexity. There is no evidence of active exploitation, public exploit code (Metasploit, Nuclei, ExploitDB), or significant community discussion, though it received limited media coverage.

Impacted Technologies

VendorProductVersion(s)CPE
5.1.1CPE matchmatch criteria
cpe:2.3:a:cisco:wide_area_application_services:5.1.1:*:*:*:*:*:*:*
5.1.1aCPE matchmatch criteria
cpe:2.3:a:cisco:wide_area_application_services:5.1.1a:*:*:*:*:*:*:*
5.1.1bCPE matchmatch criteria
cpe:2.3:a:cisco:wide_area_application_services:5.1.1b:*:*:*:*:*:*:*
5.1.1cCPE matchmatch criteria
cpe:2.3:a:cisco:wide_area_application_services:5.1.1c:*:*:*:*:*:*:*
5.1.1dCPE matchmatch criteria
cpe:2.3:a:cisco:wide_area_application_services:5.1.1d:*:*:*:*:*:*:*

CVSS Data

CVSS version used by this source: 3.0

7.5HIGH

CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Attack Vector
NETWORK
Attack Complexity
LOW
Privileges Required
NONE
User Interaction
NONE
Scope
UNCHANGED
Confidentiality Impact
NONE
Integrity Impact
NONE
Availability Impact
HIGH
Exploitability Score
3.9
Impact Score
3.6
CvssVersion
3.0

Exploit Intelligence

EPSS Score
1.93%
Probability of exploitation in next 30 days
EPSS Percentile
77.9%
Percentile rank of EPSS score among Peer Group
As of 2026-07-27
Model: v2026.06.15
This CVE's current EPSS score of 0.0193 is in the 61st percentile among its peer group of 51,506 CVEs.

Social Chatter

The average CVE in this peer group has 0.0 Twitter, 0.0 Reddit, 0.1 Bluesky, 0.1 Mastodon, and 0.4 GitHub mentions.

Media Mentions

The average CVE in this peer group has 0.1 InfoSec Media, 0.0 Vendor Blog, and 0.0 Security Researcher mentions.

Remediation

Vendor Patches (1)

ciscovendor investigatingvia nvd_reference
View patch

References

tools.cisco.com / security/center/content/CiscoSecurityAdvisory/cisco-sa-20160127-waascifs
Vendor Advisory
securitytracker.com / id/1034831